The present invention relates to conveyors in general and to 90° cross transfer conveyors in particular of the type which use two or more narrow belts that pop up between the rollers of a roller conveyor line. Ninety-degree cross transfer conveyors are often used to replace mechanical diverters which push items off a main conveyor by pushing or by striking the object being conveyed. A disadvantage of mechanical diverters is that they can damage the more delicate items in the boxes or totes which are being sorted, and move packages in only one direction.
In modern commerce, especially with the rise of the Internet and international trade, the number of packages shipped in a year is many billions and a single company may deliver over 25 million packages a day. Each package starts out from a source which may be an individual or may be a major online retailer and needs to travel across the country or around the world to an individual or business recipient. The most efficient process is to use one or more sorting regional sorting centers where packages from numerous sources are brought together and sorted into groups of packages with destinations in a limited geographical area such as a county or city. In the sorting center packages are unloaded from trucks, trains, or shipping containers onto a conveyor. As the packages move along the conveyor, optical character recognition systems or barcode readers identify the destination of each package which can then be diverted or sorted by transferring an identified package to a perpendicular path using a cross transfer conveyor. Often, especially for large shippers of packages, multiple regional sorting centers are used where the packages from the various sources are sorted according to whether the packages have a local delivery destination, or a destination served by a regional sorting center. A package may pass through more than one node of the delivery system. For overnight or air delivery, expedited shippers may use a single sorting center where all packages shipped in a particular day are transported by air, the planes unloaded, the packages are sorted, and returned on the same airplanes to their delivery destination.
When the package or item reaches a destination delivery service, the packages are again sorted according to various delivery routes and loaded onto delivery vehicles which provide the final delivery. The destination delivery services also use a conveyor arrangements to sort the packages using automated sorting systems which employ conveyors and cross conveyor diverters as means for sorting the packages for final delivery. Even within a single factory parts, often contained in totes, and finished products ready for shipping may be most economically handled by a conveyor system which sorts and delivers parts to various workstations, and collects and delivers finished products to various shipping docks from which the product is delivered to a delivery truck, a shipping container or to a collection point for a shipping service.
Conventional 90° cross transfer conveyors of the type which use a plurality of narrow belts that pop up between the rollers of a roller conveyor line generally employ belts which are like large rubber bands or O-rings that ride on pulleys attached to a vertical shelf which is raised between the rollers of the main conveyor by a pneumatic piston. In such an arrangement a package or tote on the main conveyor which is positioned over the cross transfer conveyor is engaged by the pulley supported belts when the cross conveyor shelves are driven vertically. The pop-up belts thus lift the conveyed article just above the roller conveyor line rollers. The article then rides on belts and are driven to the right or to the left at a 90° angle to the main conveyor thereby delivering the package or tote to a subsequent conveyor to the left or to the right.
In modern sorting applications, where packages can be moving 135 feet per minute (FPM) along the main conveyor, the cross transfer conveyor belts must rapidly bring the package to a stop so that the package rests on the belts and can be driven in the cross direction to a sideward downstream conveyor. The moving packages, which may weigh upwards of 100 pounds, deliver a substantial sideward force to the transfer conveyor belts when they strike them, which causes the belts to occasionally come off the pulleys on which they are supported, causing downtime for an entire main conveyor. The consequent delay in package delivery and lost work hours can be significant.
What is needed is an improved 90° cross transfer conveyor of greater reliability.